just chillin has many meanings.
the most common are when an individual really isnt gettin into shit.usually replied back when tryna chill alone.
chillin can also refer to sittin down somewhere,blazin up,wit a lil kil or maybe some good up in the cup.shit maybe even both...yeah..
the other derivative of the word is used as a reply when an individual is smokin with others or is confronted about being high,or drunk,but is not fully gone yet...just chillin.